The patch titled
Subject: lib/kasprintf.c: introduce kvasprintf_const
has been added to the -mm tree. Its filename is
lib-introduce-kvasprintf_const.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-introduce-kvasprintf_const.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-introduce-kvasprintf_const.patch
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------------------------------------------------------
From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Subject: lib/kasprintf.c: introduce kvasprintf_const
This adds kvasprintf_const which tries to use kstrdup_const if possible:
If the format string contains no % characters, or if the format string is
exactly "%s", we delegate to kstrdup_const. Otherwise, we fall back to
kvasprintf.
Just as for kstrdup_const, the main motivation is to save memory by
reusing .rodata when possible.
The return value should be freed by kfree_const, just like for
kstrdup_const.
There is deliberately no kasprintf_const: In the vast majority of cases,
the format string argument is a literal, so one can determine statically
whether one could instead use kstrdup_const directly (which would also
require one to change all corresponding kfree calls to kfree_const).
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kernel.h | 2 ++
lib/kasprintf.c | 16 ++++++++++++++++
2 files changed, 18 insertions(+)
diff -puN include/linux/kernel.h~lib-introduce-kvasprintf_const include/linux/kernel.h
--- a/include/linux/kernel.h~lib-introduce-kvasprintf_const
+++ a/include/linux/kernel.h
@@ -413,6 +413,8 @@ extern __printf(2, 3)
char *kasprintf(gfp_t gfp, const char *fmt, ...);
extern __printf(2, 0)
char *kvasprintf(gfp_t gfp, const char *fmt, va_list args);
+extern __printf(2, 0)
+const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list args);
extern __scanf(2, 3)
int sscanf(const char *, const char *, ...);
diff -puN lib/kasprintf.c~lib-introduce-kvasprintf_const lib/kasprintf.c
--- a/lib/kasprintf.c~lib-introduce-kvasprintf_const
+++ a/lib/kasprintf.c
@@ -31,6 +31,22 @@ char *kvasprintf(gfp_t gfp, const char *
}
EXPORT_SYMBOL(kvasprintf);
+/*
+ * If fmt contains no % (or is exactly %s), use kstrdup_const. If fmt
+ * (or the sole vararg) points to rodata, we will then save a memory
+ * allocation and string copy. In any case, the return value should be
+ * freed using kfree_const().
+ */
+const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list ap)
+{
+ if (!strchr(fmt, '%'))
+ return kstrdup_const(fmt, gfp);
+ if (!strcmp(fmt, "%s"))
+ return kstrdup_const(va_arg(ap, const char*), gfp);
+ return kvasprintf(gfp, fmt, ap);
+}
+EXPORT_SYMBOL(kvasprintf_const);
+
char *kasprintf(gfp_t gfp, const char *fmt, ...)
{
va_list ap;
_
Patches currently in -mm which might be from linux@xxxxxxxxxxxxxxxxxx are
lib-dynamic_debugc-use-kstrdup_const.patch
lib-introduce-kvasprintf_const.patch
kobject-use-kvasprintf_const-for-formatting-name.patch
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